The above type of cutter bar is well known and widely used in crop harvesting machines of the sickle knife type in which a knife is carried on the guards and reciprocates across the guards in a cutting action.
For some crops, the cutter bar is carried so that it skids over the ground with much of the weight of the header carried on springs but a small amount of the weight applied through the cutter bar onto the ground to hold the cutter bar against the ground in a skidding action to provide the cutting action at the lowest possible position relative to the ground.
It is well known that wear shields are mounted on the cutter bar at the position where the cutter bar contacts the ground so as to reduce the frictional wear on the cutter bar itself and to apply it instead to a replaceable plastic wear piece which can be removed when worn and replaced by a new wear piece.
Commonly such shields are bolted onto the bottom plate of the cutter bar simply by bolting through the shield into the bottom plate behind the guard bar of the cutter bar.
Examples are shown in U.S. Pat. No. 5,924,270 (Bruns) assigned to May-Wes Manufacturing Inc. and issued Jul. 20, 1999, U.S. Pat. No. 5,174,101 (Rabitsch) issued Dec. 29, 1992 and Design patent D454,576 (Huntimer) assigned to Global Polymer Industries Inc. and issued Mar. 19, 2002. All these patents show basically the same arrangement in which a sheet of plastic material is simply bolted to the underside of the bottom plate by front and rear fasteners.